This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The purpose of this study is to find out the amount of water a person needs to drink to keep blood AVP(arginine vasopressin)at a low level, and whether a person can tolerate drinking the required amount of water and not interfere with their lifestyle.